1. Field of the Invention
The present, invention relates to a wiring board having a wiring placed on a substrate, an electron source using the wiring board, an image display apparatus, and an image reproducing apparatus.
2. Description of the Related Art
Flat panel displays such as an LCD (liquid crystal display), a PDP (plasma display), and an FED (field emission display) are display apparatuses in which a lot of pixels are arranged into a plane state. Most of such display apparatuses have a wiring board provided with a plurality of wirings (X-directional wirings or Y-directional wirings) on a substrate made of glass. Some of the display apparatuses are provided with a plurality of wirings (Y-directional wirings or X-directional wirings) which cross the wirings on the substrate. Wirings are, generally, formed by applying or depositing a conductive material to or on the surface of a substrate.
Conventionally, X-directional wirings and Y-directional wirings are formed by laminating them on the smooth surface of a substrate. As high definition of displays develops, a space allowed for one pixel is required to be further reduced. In such case, if wirings are simply thinned, wiring resistance rises, and thus the thickness of the wirings for securing a conductive sectional area should be enlarged. On the other hand, when the wirings become too thick, the thickness (height) of the wirings themselves occasionally becomes a problem. Particularly in displays using an electron-emitting device such as field-emitting type and surface-conductive type ones, a trajectory of electrons emitted from the electron-emitting device is occasionally influenced by the shape of peripheral structures (for example, wirings) and an electric potential, the wirings need to be as low as possible. For this reason, a method for forming wirings in a groove which is obtained by digging down the surface of a substrate formed with the electron-emitting device is considered.